1. Field of the Invention
The present invention relates to a controlling apparatus for throttle valve in internal combustion engines, in which both an idle speed control (ISC) and an output control in response to a usual accelerator operation are controlled by a throttle valve and, moreover, relates to a controlling apparatus for driving in internal combustion engines which controls based on an open degree of a throttle valve.
2. Description of the Related Art
It is well-known that in an internal combustion engine, an intake air amount of an engine is adjusted by a throttle valve and an engine output is controlled by a throttle open degree. In controlling, a throttle valve controlling apparatus of electronically control type is known, in which both the idle speed control (ISC) and the output control in response to the usual accelerator operation is made by a single throttle valve.
In this kind of device, Japanese Patent Laid-Open Publication No.7-63083 disclosed that an idle speed control means (ISC means) for controlling a single throttle valve is provided so that an actual revolution speed of the internal combustion engine when idling becomes a target revolution speed of idling as stored beforehand based on a calculation of a throttle open degree. Further, when idling, the throttle valve is controlled by the ISC means so that the throttle open degree becomes the target revolution speed of the idling as stored beforehand.
A throttle sensor for detecting a throttle open degree is provided with the throttle valve so as to detect the throttle open degree. But a throttle open degree signal in use for engine control, etc. uses a value that a throttle fully-closed learning value is subtracted from the actual throttle open degree signal as apparent from an expression below: EQU Throttle open degree signal(TA)= EQU actual detected value of throttle sensor throttle- EQU fully-closed learning value
The throttle valve has a mechanical construction but due to assembly errors to the internal combustion engine, only detecting a throttle open degree by the throttle sensor becomes the open degree that includes the errors. Therefore, every time when starting the internal combustion engine, first, the throttle valve is fully closed and the fully-closed position is learned. Then, the throttle fully closed learning value is subtracted from the actual value which is detected by the throttle sensor so as to obtain an accurate throttle open degree.
However, in the internal combustion engine, load such as an air-conditioner, etc. is connected. In response to the size of the load, the target revolution speed of the internal combustion engine when idling is changed.
For example, the air conditioner has a compressor for refrigerant circulation, which is connected to a driving shaft of the internal combustion engine via a magnet clutch so as to drive the compressor. When the air conditioner is turned on at the time of idling, the magnet clutch is connected. But to avoid the engine to stall due to the load and to drive the compressor, the ISC means increases the target revolution speed in response to the load.
The apparatus mentioned above, in addition to the control by the ISC means, the usual control of the throttle valve by an accelerator pedal operation is conducted. Thus, when the accelerator pedal is pressed, the throttle valve is opened in response to the amount the pedal was pressed.
As apparent from the above, the actual detecting value of the throttle sensor includes a required throttle open degree balancing with the target revolution speed at the idling state. Even when the accelerator pedal is held constant, the required open degree by the ISC is changed in response to the condition of a load such as the air conditioner, etc. Thus, the throttle open degree signal is changed.
This brings great influences to various engine controls which use the throttle open degree as a controlling parameter.
For instance, when the air conditioner is turned on at the idling state, the target revolution speed increases and he target throttle open degree becomes large in response to the load of the air conditioner by the ISC means. Later, when the air conditioner is turned off, the target revolution speed when idling and the target throttle open degree are set low. However, since the actual throttle valve is open and closed by the mechanical operation, even when the target throttle open degree is set low, the throttle valve is not closed immediately because of response delay but is closed gradually.
Accordingly, when the throttle open degree is detected during the response delay, the throttle open degree is calculated which includes the delay. In other words, the throttle open degree signal subtracted the throttle full-closed learning value from the actual detecting value by the throttle sensor which detects the open degree of the throttle valve not reached to the target open degree due to delay becomes larger than the throttle open degree based on the target throttle open degree as originally required. The engine control based on the throttle open degree becomes not balancing with the originally required controlling.
Moreover, since the control by the ISC means and the throttle open degree control based on the accelerator pedal coexist, when considering from an electronic controlling by computers, the change of the throttle open degree is uncertain whether it is due to by the ISC means or by the accelerator pedal. As a result, there are some cases that engine controls in response to the accelerator pedal by the actual driver are not made. Thus, the drivability becomes bad.